Shaped Charge Jet Formation Research Articles

Research Status and Development Trend of Tandem Armor-Breaking Warheads

In order to cope with the continuous progress of tank protection technology, it is imperative to optimize and improve the ability of existing armor-breaking warheads. This paper mainly introduces the development history of explosive reactive armor, shaped charge jet formation theory, shaped charge jet penetration theory, armor-breaking warhead technology, series armor-breaking warhead technology and research status of armor-breaking/killing compound warhead technology. Finally, the development trend of armor-breaking warhead in the future is described, in order to provide some enlightenment for the design and improvement of armor-breaking warhead in the future.

Research on PTFE/Al reactive jet formation of shaped charge

During the PTFE/Al reactive shaped charge jet formation, the burst wave generated by the explosion of the explosive is sufficient to achieve the ignition conditions of the reactive materials (RMS). As a result, the RMS will react, resulting in an energy loss from the reactive jet. In order to research the forming features of PTFE/Al reactive jet and the energy loss during the jet formation, a PTFE/Al reactive liner with a diameter of 74 mm was prepared and an X-ray pulses photography experiment was performed on the jet formation. And the parameters of Johnson-Cook constitutive model of RMS were obtained through quasi-static experiments and Hopkinson pressure bar experiments. The jet formation were simulated, and the AUTODYN secondary development technology was used. The results show that the secondary development technology can intuitively show the reaction of the active material during the jet formation. The PTFE/Al reactive jet is less cohesive, its jet diameter is thicker, and the morphology is divergent. The reactive materials reacted during the PTFE/Al reactive shaped charge jet formation. And during the reactive jet formation, the inner layer of the liner collided. Therefore, most of the chemical reactions occur inside the reactive jet.

Research on non-cohesive jet formed by Zr-based amorphous alloys

The shaped charge jet formation of a Zr-based amorphous alloy and the applicability of different numerical algorithms to describe the jet formed were experimentally and numerically investigated. X-ray experiments were performed to study jet characteristics. The numerical results for the Zr-based amorphous alloy jet formed via the Euler and smooth particle hydrodynamics (SPH) algorithms were compared and analyzed using the Autodyn hydrocode. Particle motion was examined based on material properties. The Zr-based amorphous alloy formed a noncohesive jet driven by an 8701 explosive. Both the Euler and SPH algorithms achieved high accuracy for the determination of jet velocity. When the improved Johnson-Holmquist constitutive model (JH-2) was used, numerical results confirmed the model’s suitability for the Zr-based amorphous alloy. The Euler algorithm effectively reflected jet shape within a short computing time, whereas the SPH algorithm was highly suitable for showing the shape of the jet tail within a long computing time. In the 3D Euler model, the flared jet mouth indicated radial particle dispersion; however, in the 2D model, particle dispersion in the head was directly observed by using the JH-2 material model. The brittle fracture of the material reduced the proportion of particles near the liner apex forming a jet. Furthermore, a new method in which stagnation pressure was used to predict jet formation and its coherence was proposed since the collapse angle was difficult to obtain.

The Effect of Aluminum Particle Size on the Formation of Reactive Jet

In order to study the morphology characteristics of the PTFE/Al reactive shaped charge jet and the chemical reaction during the jet formation, PTFE/Al reactive liners with aluminum particle sizes of 5 μm and 100 μm were prepared. The parameters of the Johnson–Cook constitutive model of PTFE/Al reactive materials (RMs) were obtained through quasi-static compression experiments and SHPB (Split Hopkinson Pressure Bar) experiments. X-ray imaging technology was used to photograph the shape of reactive shaped charges jet at two different time points. The AUTODYN secondary development technology was used to simulate the jet formation, and the simulation results are compared with the experimental results. The results show that the simulation results are close to the experimental results, and the error is in the range of 4–8%. Through analysis, it is observed that the RMs reacted during the PTFE/Al reactive shaped charge jet formation, and due to the convergence of the inner layer of the liner during the jet formation, the chemical reaction of the jet is from inside to outside. Secondly, the particle size of aluminum powder has an influence on the chemical reaction and morphology of the jet. During the jet formation, there were fewer RMs reacted when the PTFE/Al reactive liners were prepared with 100 μm aluminum powder. Compared with 5 μm aluminum powder, when the aluminum powder is 100 μm, the morphology of the jet is more condensed, which is conducive to generating greater penetration depth.

Velocity tracking of shaped charge wire formation and propagation toward the target

ABSTRACT The formation of shaped charge jets is traditionally studied experimentally using flash X-ray and high-speed camera images. Sequential images obtained through these methods provide insight into the overall properties of the jet, such as jet tip velocity and outline shape. Numerical methods are validated using experimental results of the macroscopic properties by taking absolute velocity contours through the jet and comparing the outline shape. These methods do not describe where, and in which order, discrete parts of the shaped charge liner are located in the jet after formation. Shaped charge jet formation is studied here numerically by tracking the velocity in the flow field using stationary gauges and by placing dynamic gauges on the shaped charge liner. This method provides insight into the physical mechanism of jet formation. It is generally assumed that the shaped charge jet forms from liner inversion, where the liner tip becomes the jet tip that first penetrates the target. This work shows that the liner tip does not form part of the jet but is rather absorbed into the slug. Similarly, PER theory assumes that the outer part of the liner (next to the explosive) flows into the slug and the inner part flows into the jet. It is shown here that this assumption is not valid in all cases. This study is a proof of concept to highlight the advantages of using the method of simultaneous liner and flow field velocity tracking to aid shaped charge optimization activities.

Effect of fragment impact on shaped charge jet formation and penetration into steel target

Purpose This paper aims to investigate the effects of fragment impacts to shaped charge warheads in terms of shaped charge jet formation geometries and penetration performances. Design/methodology/approach In experimental process, a fragment was accelerated to a shaped charge warhead by means of a powder gun to a velocity more than 1,000 m/s, and this impact led to conical damage in the explosive of the warhead. Deformation on the warhead was visualized using X-ray technique to observe holes generated during fragment impact. Penetration test was performed against AISI 1040 steel plates with the damaged shaped charge warhead. Penetration performance of shaped charge jet, which deviated from the symmetry axis, was simulated by using SPEED software with 3-D Eulerian method to validate the numerical modelling method by comparing penetration test and simulation results of damaged warhead. Findings Simulation and test results showed good correlation for the warhead in terms of penetration depth and hole geometry at the impact surface of steel plates. In addition, the effects of the numbers and the geometries of fragment holes on shaped charge jet penetration performances were investigated with validated numerical methods. Simulation results showed that the increase in the number of fragment holes in the explosive of the warhead led to particulation of shaped charge jet that diminished penetration depth in the target plate. Additionally, simulation results also showed that the fragment hole geometry in the explosive after different fragment impact angles affected the amount of jet deviation from the symmetry axis as well as penetration depth in the target plate. Practical implications The results obtained from the current study revealed that fragment impact angle and different number of fragment impact reduced the penetration performance of shaped charge warhead by influencing the symmetry of shaped charge jet negatively. Originality/value The current study fulfils the need to investigate how fragment impact on the shaped charge warhead affect the formation symmetry of shaped charge jet as well as penetration performance by experimental and numerical methods. Penetration performance result of asymmetric jet is compared by experimental and numerical studies. A detailed methodology on numerically modelling of the effect of fragment impact angle and number of fragment impact on shaped charge jet performance is given in this study.

Effect of Controlled Perturbations on Buckling of a Conical Liner during Shaped-Charge Jet Formation

Effect of Controlled Perturbations on Buckling of a Conical Liner during Shaped-Charge Jet Formation

Experimental and Numerical Study on the PG-7VM Warhead Performance against High-Hardness Armor Steel.

Analyses presented in the article were carried out in order to characterize the main parameters of the shaped charge jet formed due to detonation of the PG-7VM warhead. As opposed to the previously published studies in which rolled homogeneous armored steel was mainly used as a target, in the current work the warhead penetration capability was determined against more contemporary high-hardness (500 HB) ARMSTAL 30PM steel armor with precisely determined mechanical properties. The research included experimental depth of penetration tests and their numerical reproduction in the LS-Dyna software. Special attention was paid to factors that could perturbate the shaped charge jet formation process and under- or overestimate its penetration capability. For this reason, warheads were X-ray inspected for structural discrepancies (voids or air inclusions in explosive, misalignment between the body, explosive, and liner, or lack of contact between the explosive and the liner) and properties of materials (explosive, targets, and most important warhead components) were analyzed before the experiments. The numerical model of the warhead was defined more accurately than in previously published studies, since it was based on the real grenade dimensions and its technical documentation. Thanks to this, the depth of penetration of the target made of ARMSTAL 30PM armored steel plates by the shaped charge jet formed from the PG-7VM warhead obtained by numerical simulation was consistent with the experimental results and equaled 278 mm and 280 mm, respectively. The difference between the experimental and numerical value was smaller than 1%, which confirms that the developed methodology of modeling allows users to properly reproduce the PG-7VM shaped charge jet formation and target penetration processes. A verified numerical model of the shaped charge jet penetration into a steel target was used to determine depth of penetration in function of stand-off distance for the PG-7VM warhead. A maximum depth of penetration of about 317 mm was obtained for the stand-off distance of 360 mm, which may indicate the potential direction of modernization of warheads.

Effect of Controlled Perturbations on Buckling of a Conical Liner During Shaped-Charge Jet Formation

Effect of Controlled Perturbations on Buckling of a Conical Liner During Shaped-Charge Jet Formation

Kinematics of the shaped charge jet formation process

Based on the review of scientific and technical literature, an analysis is made of the problems of the modern theory of formation, extension and destruction of the shaped jet. The focus of the research is on the kinematics of the formation of a shaped jet based on the approach of operating with the characteristics of a real metal when the velocity vector of the cumulative jet is the result of three vectors: strain, strain and displacement of the shaped jet’s material. The numerical experiment of the functioning of the shaped charge is carried out, and the procedure for evaluating the calculation results is proposed. The obtained data correlate with existing knowledge about the physics of the cumulation process.

Numerical simulation to determine the shaped charge jet-slug interface

In order to determine the interface of shaped charge jet-slug, numerical simulation of the shaped charge jet forming process is carried out by non-liner finite element numerical simulation. A plurality of gauge points is arranged in the thickness of the liner, and the velocity and pressure time history of different gauge points is obtained in the jet forming stage. The result show that in the process of shaped charge jet formation, obvious velocity and pressure difference in gauge point is observed. By dividing the boundary between the slug and jet of different sets of gauge points, the corresponding area of jet and slug can be determined on the liner. The numerical simulation to determine the shaped charge jet-slug interface can be used to evaluate the performance of different shaped charge design and provide guidance for shaped charge design.

Instability of a Conical Liner during Shaped-Charge Jet Formation

Instability of a conical liner during shaped-charge jet formation has been studied. To establish the metal flow pattern during shaped-charge jet formation, we fabricated three-layer copper-copper-Constantan liners consisting of a solid copper conical cone with a cone angle of 45°, a wall thickness 1.5 mm, and a cone pressed into it and rolled from a copper sheet 1.0 mm thick clad on the inside with Constantan 0.2 mm thick by explosive welding. Liner compression was carried out by an RDX charge 20 mm thick. The jet formation process was recorded by flash radiography, and the metal flow pattern was determined by micro sections of recovered slugs. Since the interface between the explosively welded metals is clearly distinguishable in the sections, the residual deformation in different sections of the slug shows the occurrence of liner instability during the compression, which manifested itself as folds oriented along the generatrix of the cone. At the same time, the general flow pattern described in terms of the theory of an ideal incompressible fluid is not disturbed, which follows from radiographs of the shaped-charge jet formation process.

Numerical Analysis of the Formation of Shaped-Charge Jets from Charges with Conical and Semi-Spherical Liners of Variable Thickness

Studies of shaped charges with hemispherical liners of degressive thickness (decreasing from the top to the base) were continued based on numerical simulation. The possibility of increasing not only the velocity but also the mass of the head elements of shaped-charge jets to the level provided by conical liners of progressive thickness were analyzed. For this purpose, liners of degressive thickness in the form of a truncated sphere and a semi-ellipsoid slightly elongated along the charge axis were additionally studied.

Instability of a Conical Liner during Shaped-Charge Jet Formation

Instability of a Conical Liner during Shaped-Charge Jet Formation

Numerical Analysis of the Formation of Shaped-Charge Jets from Charges with Conical and Semi-Spherical Liners of Variable Thickness

Numerical Analysis of the Formation of Shaped-Charge Jets from Charges with Conical and Semi-Spherical Liners of Variable Thickness

Generation of Hypervelocity Particle Flows by Explosive Compression of Ceramic Tubes

The compression of ceramic (corundum) tubes by the detonation products of explosives have been studied experimentally and numerically. The formation of the shaped-charge jet of ceramic particles and its effect on steel witnesses targets has been investigated. The tubes were produced by detonation spraying. Ceramic particles were deposited on copper tubes, which were then dissolved in a solution of ferric chloride. In the experiments, a considerable penetration of the flow of ceramic particles was observed. During the interaction of the flow with the target, the target material was partially evaporated, as shown by metallographic analysis. Numerical analysis of the formation of the discrete shaped-charge jet showed that the maximum velocity of the jet head was about 23 km/s, and the velocity of the main part of the jet was about 14 km/s.

Сравнительный анализ формирования кумулятивных струй из конических и полусферических облицовок

Сравнительный анализ формирования кумулятивных струй из конических и полусферических облицовок

Investigation on shaped charge jet density gradient for metal matrix composites: Experimental design and execution

A novel experiment combined with projection method was developed to investigate the composition and density gradient of composite materials during the shaped charge jet formation process. Shock Physics Explicit Euler Dynamic (SPEED) simulation was applied to clarify the jet formation and penetration with built-in offset initiation in order to verify the validation of the experimental system. Tungsten-copper (W-Cu) liner was selected as a specific example for the experiment design and execution in this paper. The microstructures of the W-Cu jet recovered from the target surface were observed by scanning electron microscope (SEM). Meanwhile, Cu contents were detected by energy dispersed spectrum (EDS) along the penetration trail. The result shows that Cu contents vary with positions in the jet and density defects occur in the jet with a maximum of about 10% reduction at the jet tip. The relation between jet densities and positions was successfully established, providing a good basis for the shaped charge penetration calculation in the future work.

A Numerical Method for the Determination of the Virtual Origin Point of Shaped Charge Jets Instead of Using Flash X-ray Radiography

ABSTRACTThe effective jet length between the virtual origin (VO) point and the target surface is very important for the calculation of a shaped charge jet penetration. A numerical approach to determine the exact position of the VO of a small caliber shaped charge jet is presented in this paper. The numerical approach includes shaped charge jet formation algorithm using explicit Autodyn solver and estimates the precise location of the VO point using the hydrocode analysis. This is particularly important when the experimental flash X-ray radiograph is not available. The proposed VO model approach was validated by firing four small caliber shaped charges against concrete targets. The maximum difference between the experimental penetration depth and that calculated using the presented VO approach was less than 4%.

Numerical simulation of the formation of shaped-charge jets from hemispherical liners of degressive thickness

The formation of shaped-charge jets from hemispherical copper liners of degressive thickness (decreasing from apex to bottom) is analyzed by numerical simulation of a twodimensional axisymmetric problem of continuum mechanics. The comparison was based on the parameters of the jet formed from a modern standard shaped charge with a conical liner which provides penetration of a steel target to a depth equal to 10 charge diameters. The comparative analysis was performed using calculated mass–velocity distributions and the ultimate jet length–velocity distributions obtained on their basis, from which the potential penetrability of jets was evaluated. It is shown that the shaped-charge jets formed by hemispherical shaped-charge liners of degressive thickness are comparable in head velocity and penetrability to the jets from conical liners.